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This paper presents an experimental study of the behaviour of the mass loss rate (MLR) of pool fires in mechanically ventilated compartments within the framework of fire research activities conducted at the French Institute for Radiological Protection and Nuclear Safety (IRSN). Two typical scenarios are investigated: the 1-room configuration and the 2-rooms configuration with an open doorway between the two rooms. This study is based on full scale tests carried out as part of the international OECD PRISME project (OECD: Organisation for Economic Co-operation and Development; PRISME: French acronym for “Fire Propagation in Elementary Multi-room Scenarios”). First the behaviours of the MLR for the two scenarios are presented independently. A comparison is then proposed that highlights the effect of the air change rate on the MLR. The analysis shows that the MLR depends on two effects: the oxygen concentration and a blowing effect towards the pool. For most tests, the effect of oxygen concentration is predominant and the MLR varies linearly with the change of oxygen concentration. For one test with the 2rooms scenario, the air flow at the door seems to induce higher oxygen level adjacent to the pool and the MLR is identical to that in the open air, albeit with an oxygen concentration below 21%vol; In this configuration, the air flow at the door may induce not only a locally higher oxygen level, but also a blowing effect that stokes the fire. This large-scale test campaign shows that the air flow around the pool is also an important parameter to predict the MLR.

Several test methods commonly employed to rate the combustibility of materials are evaluated and compared to criteria for the stability of flaming combustion in the firescience literature. These science-based criteria are then used to analyze measurements and visual observations obtained when four prototype “noncombustible” materials are tested in the Fire Propagation Apparatus (ASTM E 2058). Based on this analysis, it is proposed that observation of the presence of flame and measurement of heat release rate at an applied heat flux of 50 kW/m and an inflow oxygen concentration of 40% can be used to determine whether a material should be rated as “noncombustible.”

In this paper we present some early work concerned with the development of a simple solid fuel combustion model incorporated within a Computational Fluid Dynamics (CFD) framework. The model is intended for use in engineering applications of fire field modelling and represents an extension of this technique to situations involving the combustion of solid cellulosic hels A simple solid &el combustion model consisting of a thermal pyrolysis model, a six flux radiation model and an eddydissipation model for gaseous combustion have been developed and implemented within the CFD code CFDS-FLOW3D The model is briefly described and demonstrated through two applications involving fire spread in a compartment with a plywood lined ceiling. The two scenarios considered involve a fire in an open and closed compartment The model is shown to be able to qualitatively predict behaviours similar to flashover - in the case of the open room - and backdrafl - in the case of the initially closed room.

The Fire Propagation test, BS 476, Part 6 was developed to assess a lining material's potential contribution to fire growth in an enclosure based on the material's notional heat release profile and is assessed by means of indices derived from measurements of the flue gas temperature. The apparatus was modified to include measurements of mass loss and oxygen consumption to enable calculation of heat release parameters. Air flows into the naturally ventilated enclosure systems were derived from exhaust gas measurements and variations in system combustion efficiencies were identified. Investigations reveal that the Fire Propagation test environment addresses crucial features of a wall lining's heat contribution to a dynamically changing fire environment in enclosures. The derived test performance indicators reflect in a single test, the fire response characteristics of the material with respect to the three generic material types tested, namely, plasterboards, fire retarded and untreated woods.

Results are presented for the vertical fire propagation for 0.508 and 1.29 m long electrical cables in oxygen concentrations of 40 and 30%, respectively. The bottom 40% of the 0.508 m long cable and 16% of the 1.29 m ~ong cable are exposed to external heat flux with a peak value of 50 kW/m. In the experiments, measurements are made for heat release rates, generation rates of chemical compounds and optical density of smoke. The vertical fire propagation rate for cables is found to be proportional to the ratio of the chemical heat release rate to thermal response, a relationship suggested by various fire propagation theories. Conditions where self-sustained fire propagation is not expected to occur have been identified: 1) critical or minimum heat flux for ignition> 20 kW/m2; 2) vertical fire propagation rate V < 1.0 x 103 m/s; and 3) chemical heat release rate/thermal response-< 0.55 secl 12 . These conditions are satisfied in larger-scale fire propagation experiments for cables. The analysis suggests that it is possible to design a small-scale standard fire test for cables based on ignition, fire propagation and heat release rate.

The development of a methodology for the quantification of the risks associated with fires in nuclear power plants requires the use of judgment, deterministic models and statistical evidence. Several issues that arise are discussed including: 1. The impact of design changes, plant-to-plant variation and other qualitative factors on the assessment of the frequency of fires in specific locations; 2. The importance of distinguishing among statistical, parameter and modeling uncertainties, when fire propagation is studied; 3. How parameter and modeling uncertainties can be assessed; and 4. How the probability distribution of detection and suppression times can be determined.